The invention relates to an open end friction spinning machine with a plurality of adjacently arranged spinning units, each having a pair of friction rollers driven in the same rotational direction and disposed to form a yarn forming wedge slot therebetween.
It is known (EP-OS 52 412) that the rollers of friction spinning units from time to time must be cleaned, especially after a thread break. With the known construction, it is therefore provided that one of the friction rollers can be moved away from the other so that the friction rollers and the wedge slot formed by them is accessible for a manual cleaning process. Such an arrangement exhibits disadvantages in that this work is tedious and the results are dependent upon the care of the servicing person. This construction also demands a high manufacturing expenditure, especially for the bearings for the rollers, because it is essential that the rollers are so carried that they maintain the exact relative bearing position when moved to their driving position. If the rollers are to be moved relatively to one another, the guide mechanism for this movement must therefore be provided with very close tolerances so that the indicated demands are fulfilled.
The invention is based upon the problem to create the possibility, with open end friction machines of the above-mentioned kind, to permit a cleaning of the rollers in a proper manner which is simple to accomplish and the results of which are not dependent upon the care of the servicing person.
These problems are thereby solved according to the present invention, in that pneumatic cleaning devices are provided to clean the rollers.
Because pneumatic devices are necessary for the operation of the open end friction spinning machine anyway (e.g., in conjunction with creating air flow for transport of fibers to the wedge slot), the additional expense for the provision of pneumatic cleaning devices is relatively small. The cleaning devices always function in the same manner so that the quality of the cleaning is not dependent upon the care of the servicing person. The pneumatic cleaning devices make it unnecessary for the rollers to be moved from their relative spinning positions for the cleaning process, thereby substantially simplifying the design demands for the rollers' bearings. In preferred embodiments, activation of the pneumatic cleaning devices occurs whenever the spinning procedure is interrupted, for example, after a thread break, after a spool change, or after a change of the material to be spun. The invention also contemplates embodiments which facilitate preventive servicing and cleaning operations for the rollers. Such embodiments can be automatically or otherwise controlled to clean the rollers after a predetermined running time of the rollers and/or after the production of a predetermined volume or length of yarn.
In practical embodiments of the invention, at least one cleaning nozzle is provided for each roller, which nozzle is connected at an overpressure source and/or underpressure source by means of pneumatic lines which contain activating and/or switch over valves. Such embodiments are especially advantageous if one is using hollow friction rollers with perforated cover surfaces, wherein fiber fly, fiber dust and/or fiber residue is deposited inside of the rollers. These contaminants can be loosened and removed with the pneumatic cleaning arrangements of the invention, especially by alternating between overpressure and underpressure via the nozzles. In especially preferred embodiments of the invention, it is advantageously provided that the cleaning nozzles are formed as slot nozzles extending over approximately the length of the rollers.
In advantageous embodiments of the invention, it is provided that a cleaning nozzle is disposed at the wedge slot formed by the rollers. Such a cleaning nozzle, which preferably is connected at an underpressure source, can also be advantageously used during a start spinning procedure, for example, in order to transport away the fibers which are not desired and which are returned by a fiber feeding and opening device, before the actual start spinning process.
In further embodiments of the invention, it is provided that a cleaning nozzle is arranged at the circumference of each roller. This arrangement is especially advantageous with hollow rollers with perforated cover surfaces because it facilitates removal of the contaminants which deposit inside of the rollers during spinning operations. It is advantageously provided in certain embodiments that the cleaning nozzles are arranged at the circumferences of the rollers and are connected at an overpressure source. Thereby it is possible to loosen the contaminants by high pressure air and then to suck them off through a further cleaning nozzle connected to an underpressure (vacuum pressure) source.
In still further embodiments of the invention, a travelling maintenance unit is provided which is adjustably movable to each of the spinning units and which is outfitted with apparatus for activating the pneumatic cleaning nozzles. Thereby it is achieved that not only the quality of the cleaning, but also the accomplishment of the cleaning is automated so that improper servicing is avoided.
In further embodiments of the invention it is provided that the maintenance unit is provided with mechanisms for interrupting the operational drive of the rollers at the spinning unit to be cleaned. It is especially advantageous if the maintenance unit is further provided with adjustable means to drive the rollers at the respective spinning units. Thereby it is possible to loosen the rollers from the drive for the spinning operation and additionally to drive the rollers with a more suitable velocity for the cleaning operation.
Further objects, features, and advantages of the present invention will become more apparent from the following description when taken with the accompanying drawings which show, for purposes of illustration only, an embodiment in accordance with the present invention.